Electric valve apparatus



Oct. 24, 1944.

C. H. WILLIS ELECTRIC VALVE APPARATUS Filed Nov. 26, 1942 Inventor:Clodius H. Willis,

His Attorney.

Patented Oct. 24, 1944 UNITED STATES PATENT OFFICE ELECTRIC VALVEAPPARATUS York Application November 26, 1942, Serial No. 467,033

6 Claims.

My invention relates to electric valve apparatus and more particularlyto electric valve apparatus adapted for transferring power between aplurality of circuits, at least one of which is a polyphasealternating-current circuit.

Electric valve apparatus has been widely used in industrial applicationsfor transferring controlled amounts of power between supply and loadcircuits of different electrical characteristics. The valve meansemployed have been of two general types, one, the multianode tank inwhich a plurality of anodes supported within a container or vesselcooperate with a single mercury pool cathode and the other of which iscommonly called a single-anode tank and comprises a single anode, and asingle mercury pool-type cathode. The multianode units have had someadvantages with respect to the number of units required and the cost ofconstruction. However, these units have been subject to certainoperating disadvantages, such as a tendency for the arc to form betweenone of the anodes and a wall of the container. As a result of thesedisadvantages, the trend has been toward the single-anode unit. Whilethese single units have in many respects exhibited superior operatingcharacteristics, the control and excitation equipment required forestablishing a cathode spot once each cycle for each of theanode-cathode circuits has required a large amount of equipment ofsizable electrical rating. This is particularly true in installationsutilizing the immersion-ignitor type of control member for initiatingthe cathode spot. In accordance with the teachings of the presentinvention, I provide new and improved electric valve apparatus utilizingelectric valve means of the multianode type which, to a considerableextent, combines the advantages of both the multianode and single-anodetypes of electric valve means.

It is an object of my invention to provide new and improved electricvalve apparatus.

It is another object of my invention to provide a new and improvedelectric valve system having dependable operating characteristics and,at the same time, requiring a minimum of excitation and controlequipment in its operation.

In accordance with the illustrated embodiment of my invention, I haveshown a double threephase electric valve system interconnectingalternating and direct-current circuits. Two electric valve means, eachincluding three anodes and a mercury pool cathode, are employed and theanodes of each valve means are connected with the phase terminals of thesupply in such a manner that there is a considerable period during eachcycle of alternating-current voltage that each of the valve means isdark, or, in other words, during which all of the discharge paths of thevalve means are nonconductive. An immersion-ignitor type of controlmember is associated with each of the valve means for establishing acathode spot once during each cycle of the alternating-current voltage.Control members or grlds'are associated with each of the anodes tocontrol the instant of imitation of conduction in each of the dischargepaths.

My invention will be better understood by reference to the followingdescription taken in con nection with the accompanying drawing and thescope will be pointed out in the appended claims. In the drawing, Fig. lis a schematic representation of one embodiment of my invention and Fig.2 represents the conducting periods of the various anodes of theelectric valve means illustrated in Fig. 1.

Referring now to the drawing, I have shown my invention embodied in anelectric valve system for transferring current between a polyphasealternating-current circuit In and a direct-current circuit comprisingconductors II and I2. Throughout the remainder of the specification, thesystem will be described as a rectifier operating to transfer energyfrom the alternating-current circuit H) to the direct-current circuitll, l2, although it will be understood that the system may readily beoperated to transfer energy in either direction. A transformer l3 havinga delta-connected primary winding H energized from thealternating-current circuit 10 is provided with two groups of -connectedsecondary windings l4 and I5 having the neutral terminals thereofinterconnected by an interphase transformer IS. The direct-current lineH is connected to an intermediate terminal on the interphase transformerHi. The phase terminals of the windings I4 and I5 are arranged to beconnected selectively with the direct-current conductor l2 by means ofthe discharge paths of electric valve means H and I8 which are identicalin construction and each comprises a container 19 which provides ahousing for the electrodes. As illustrated in the drawing, the valvemeans I! and I8 each include three anodes which have been designated 20,2!, 22 and 23, 24, 25 respectively, a mercury pool cathode 26, amake-alive electrode 21 which has been illustrated as theimmersion-ignitor type, and a relieving anode 28 and control members orgrids 2811. As is well understood by those skilled "in the art, thecontainers H are either permanently sealed oil to form a vacuum-tightenclosure or are arranged to be connected with an evacuating system.

In order to provide a cathode spot in the devices l1 and IB once eachcycle, the starting electrodes 21 and relieving anodes 28 are energizedfrom a suitable peaked voltage-producing circuit 29 which, asillustrated, may be energized from the alternating-current supplycircuit through any suitable phase-shifting device which has beenillustrated schematically at 33. The excitation circuit 29 comprises acapacitor 31 connected across the secondary winding 32 of a transformer33 having the primary winding 34 thereof energized from the adjustablesingle-phase output of the phase-shifting device 30. A self-saturatinginductive reactance 35 and a midtapped linear inductive reactance 38 areconnected in series relation across the terminals of the capacitor II.The midtap of the reactor 35 is connected to the cathodes 28 of valvemeans I! and I8 through the direct-current line 12 and the end terminalsof reactor 36 are connected with the relieving anodes 28 and thestarting electrodes 21 of the valve means I1 and 18, respectively.Connected in series with each of the starting electrodes 21 is aunilaterally conducting device 31 and a resistor 38 which aids intransferring current from the starting electrode to the relieving anodeupon the formation of a cathode spot. The excitation circuit justdescribed is disclosed in detail and claimed in the copendingAlexanderson et al. application, Serial No. 374,716, filed January 16,1941, and assigned to the assignee of the present invention. As will bereadily appreciated by those skilled in the art, the excitation circuitis eifective to impress voltages of peaked wave form on the startingelectrodes 21 of devices I! and II at intervals displaced 180 electricaldegrees and that the phase position of the peaked voltages may beadjusted with respect to the supply circuit It by means of thephase-shifting device 30.

In order that the instant of initiation of conduction of each of thedischarge paths of the electric valve devices I1 and I! may beaccurately controlled, I provide a biasing battery 39 and a transformer40 for energizing the control members or grids 28a. The transformer 40is provided with a primary winding 4! energized from thealternating-current circuit I through a suitable phase-shifting device42 and with a secondary winding 43. The winding 43 is provided with aneutral terminal connected with the cathodes 26 through battery 39 andwith six phase terminals for connection with the control members 28aassociated with anodes 20 to 26, respectively, only one has been shownconnected in order to simplify the drawing. The battery 33 impresses anegative voltage on each of the control members to maintain each of theelectric discharge paths nonconductive until a predetermined instant inthe cycle of anode-cathode voltage thereof determined by the adjustmentof the phase-shifting device 42.

It will be noted from an inspection of the drawing that anodes 20 and 2|are connected with phase terminals of winding 14' while the anode 22 isconnected with the phase winding of the secondary winding ii. In otherwords, the three anodes of the electric valve device H are connected tobe energized with voltages having such a phase relation that all of theconduction in the device l1 takes place within a period of substantially240 electrical degrees duration. As a result, there will be no arc inthe device I! for substantially 120 electrical degrees. The anodes ofthe valve device I! are similarly connected to provide a substantialperiod during which all of the discharge paths are nonconductive. Thisarrangement of connections is illustrated schematically in Fig. 2 inwhich the periods of conduction of each of the anodes of the devices I1and II have been designated by the primed numeral designating thecorresponding anode. It has been found that such an arrangement whereinthe arc is initiated every cycle overcomes the tendency of the arc toform between one of the anodes and the wall of the container whichexists in conventional multianode electric valve circuits utilizingmultianode electric valve units. At the same time, the excitation orcontrol equipment required for forming the cathode spot has beenmaterially reduced, inasmuch as one double peak-producing circuitfurnishes the excitation for the ignitors of a six-phase or six-anodesystem as compared with three times this equipment required for theexcitation of six single-anode electric valve means. The power consumedby the control members or grids 23a is comparatively small and thisequipment is of much smaller electrical rating than the excitationequipment required for the starting or immersion-ignitor electrode.

Although the illustrated embodiment of my invention relates to a doublethree-phase rectiiler circuit, it will be understood that my inventionin its broader aspects is applicable to any polyphase electric valvesystem regardless of the number of phases or whether an interphasetransformer is employed.

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that changesand modiflcations may be made without departing from my invention in itsbroader aspects, and I, therefore, aim in the appended claims to coverall such changes and modifications as fall within the true spirit andscope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a polyphase alternatingcurrent circuit, a secondcircuit, electric translating apparatus interconnecting said circuitsand including electrically displaced windings for producing twosymmetrical polyphase systems of voltage, and a plurality of electricvalve means each including a plurality of anodes and a single cathode,means connecting the anode-cathode circuits of said electric valve meanswith different phases of said windings in such a manner that the systemof voltages impressed on the anode cathode circuits of each of saidvalve means is unsymmetrical so that during normal operation there is asubstantial period during each cycle of said alternating-current circuitthat all of the anodes of one of the electric valve means aresimultaneously negative with respect to the cathode thereof.

2. In combination, a polyphase alternatingcurrent circuit, adirect-current circuit, a plurality of electric valve meansinterconnecting said circuits, each of said valve means including aplurality of anodes and a single cathode, means connecting theanode-cathode circuits of said electric valve means with phases of saidpolyphase circuit displaced with respect to each other by such an amountthat all of the anode-,cathode circuits of one of the valve means aresimultaneously non-conducting as a result of the anodecathode voltagesfor a substantial portion of each cycle of voltage of saidalternating-current means so that during each cycle of voltage of saidalternating-current circuit there is a substantial period during whichmore than one anode-cathode circuit in each of said valve means areconducting simultaneously and a substantial period during which there isno conduction in each of said valve means.

4. In combination, a polyphase alternatingcurrent circuit, a secondcircuit, electric translating apparatus interconnecting said circuitsincluding a pair of electric valve means each having a plurality ofanodes, a control member associated with each anode, a cathode, and anelectrode associated with the cathode for forming a cathode spot, meansfor energizing the anode-cathode circuits from said polyphasealternating-current circuit with voltages having such a phase relationthat there is a substantial period during each cycle of voltage of saidalternating-current circuit during which all of the anodes of one of theelectric valve means are simultaneously negative.

with respect to the cathode thereof, means for energizing the electrodeassociated with said cathode to form a cathodespot during each cycle ofvoltage ofsaid alternating-current circuit, means for impressing avoltage on the control members associated with said anodes formaintaining all oi the anode-cathode circuits nonconductive, andmeansfor impressing a second voltage on said control members forrendering the anode-cathode circuits selectively conductive.

i. In combination, a polyphase alternating current circuitya secondcircuit, electric translating apparatus interconnecting said circuits,including at least four electrically displaced phase windings, a pair ofelectric valve means each including at least two anodes, a singlecathode, an electrode associated with said cathode, and a control memberassociated with each of said anodes, means connecting said anodes withsaid electrically displaced phase windings in such a manner that thevoltages impressed on the anodecathode circuits of each of the electricvalve means are unequally displaced electrically with respect to oneanother, means for energizing the electrode associated with said cathodeto establish a cathode spot, and means for energizing the controlmembers associated with said anodes for controlling the instant ofinitiation of conduction of each of the anode-cathode circuits of saidvalve means.

6. In combination, a polyphase alternatingcurrent circuit, adirect-current circuit, electric translating apparatus interconnectingsaid circuits including a plurality of groups oi electrically displacedphase windings and a plurality of electric valve means each having anumber of anodes equal to the number 0! phase windings in one of saidgroups and a single cathode, means connecting said phase windings andsaid valve means between said circuits to operate as a double polyphasevalve-converting system, the anodes of each of said valve means beingconnected with respective phases of more than one of said groups ofwindings so that the voltages impressed on the anodes of any one of saidvalve means are notequally displaced electrically with respect to oneanother, means for establishing a cathode spot in each oi said valvemeans once during each cycle of voltage of said alternating-currentcircuit, and means associated with each of said anodes for determiningthe instant of initiation of conduction in each of the anode-cathodecircuits.

CLODIUS H. WILLIS.

